Product-type relay



Patented Dec. 25, 1951 PRODUCT-TYPE RELAY William K. Sonnemann, Roselle Park, N. J., as-

signor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsyl- Vania Application June 20, 1950, Serial No. 169,235

10 Claims. 1

My invention relates to a wattmetric or product-type relay and an energizing-network therefore, having two input-currents of the same frequency, or even two alternating currents of different frequencies. The network which energizes the relay is so designed that it produces a positive or operative torque for actuating the relay in response to one of the input-currents, which I call the operating current, while producing a negative or restraining torque for restraining the relay-operation, or for moving the rotor-element in the opposite direction, in response to the other input-current, which I call the restraining current. Preferably, this opposed-torque action is obtained in such a manner that the responses are not affected by the relative phase-angle between the operating current and the restraining current.

My invention is applicable both to high-speed relays and to slow-speed relays in which the speed of the response varies significantly with the conditions which produce the relay-operation. My improved relay-assembly may be used either as a differential-current relay, or as a ratioor percentage-differential relay, or as an impedance relay, or in fact in any relay in which an operating torque and an opposing or restraining torque or force is required.

With the foregoing and other objectives in mind, my invention consists in the systems, circuits, combinations, apparatus, parts, and methods of design and operation, hereinafter described and claimed, and illustrated in the accompanying drawing, wherein Figure 1 is a diagrammatic view of a wattmetric or product-type relay-element and an energizing network therefor in accordance with my invention,

Fig. 2 is an equivalent circuit diagram of the essential energizing-connections, and

Figs. 3, 4 and 5 are application-diagrams showing representative external-circuit connections for using my relay as a diiferential-current relay, a percentage-diiferential relay, and an impedance relay, respectively.

In Fig. 1, a wattmetric or product-type relayelement is indicated at I, having two stationary windings Z1 and Z2, and having a rotormember 2 carryin a contact-making member 3. The windings Z1 and Z2 are connected in a bridge-circuit having the corners m, n, o, p, with the winding Z1 connected in the bridgeleg mn, a resistance R connected in the bridge- ,leg no, the other winding Z2 connected in the bridge-leg op, and a reaQtaIiGQ-QQ L wh ch s represented by its resistance Rx and reactance 7X, connected in the fourth bridge-leg pm. An input-circuit, having terminals 4 and 5, is provided, whereby an operating current Io may be led into the corner 1n, and out of the diagonally opposite corner 0 of the bridge. A second input-circuit, having terminals 6 and I, is provided, whereby a restraining current Ir may be led into the corner p, and out of the diagonally opposite corner n of the bridge. A controlled circuit, having terminals 8 and 9, is also provided, in which the relay-contact 3 is connected, as is well understood in the relaying art.

The equivalent energizing circuits are shownin Fig. 2, in which I have indicated the relaycurrents I1 and I2 as flowing in the respective relay-windings Z1 and Z2, and these windings are indicated as having impedances (Ri-l-yXi) and (R2-l-7'X2), respectively. The resistances Rx, R1 and R2 are all small as compared to the resistance R and the reactances X, X1 and X2.

In the explaining the derivation of the network-constants and the performance-characteristics of my relay-assembly. I will first, as sume that the relay I is a sine-angle relay, or a product-type relay in which the torque or relay-force is proportional to the product of the currents I1 and I2 traversing the respective relay-windings Z1 and Z2, multiplied by the sine of the angle c by which the current I1 in the first winding Z1 leads the current I2 in the second winding Z2, using the usual convention whereby a dot over a symbol indicates a com plex number, whereas the symbol without the dot represents either the vector generally, without reference to its phase-angle, or the scalar or absolute magnitude-value of the vector. In the sine-type relay l, the relay-torque is T:I1I2 sin (1) This assumption of a sine response-characteristic does not mean that my invention is not applicable to awattmetric or product-type re lay having any other characteristic angle of response, such as a sin (:q) response, because, in such a case, all that would be necessary would be to rotate the phase-angle'oi" one or both of the relay-currents I1 or I2, or the corresponding relay-fluxes, through an angle or angles totalling i-q to compensate for the characteristic angle q of the relay, and then treat the relay as if it were a sine-angle relay. Various phase-shifting means are known for such a purpose, such as a short-circuited laggingcoil, a shunt-connected impedance, or some other phase-shifting network, associated with one or both of the relay-windings Z1 or Z2. Hence, I shall explain the design of my bridgenetwork as if the relay I is a sine-angle relay, having the torque-characteristic stated in Equation 1, with the understanding that I am not limited to the use of this precise type ofrelay.

Let usdesignate the phase-angles ofx'the two input currents IO and Ir of the network as 60 and 01', respectively, so that the operating cur rent is tor angle of the branch mno compared to the branch mp of the bridge. The second inputcurrent, Ir, isalso divided into two dissimilar components B11- and D11, for application to the two winding-currents I1 and I2, respectively, but now the component BI! which flows through the first winding Z1. lags behind the component DIr which flows through the second winding Z2. Consequently the first relay-winding Z1 is energized with a phase-advanced component AIO which is divided from the first input;current I0, and a phase-retarded component BIT which is divided from the second input-current, while the secjo=lo oo (2) I and the restraining current is jr=Ir L 0r (3) and let us designate, by 0, the angle by which the restraining current Iileads the operating" current Io, so that In tfi pridg-ilitwork or Fig. 2, the two input currents It and Ir divide in the inverse ratios of the impedances of their paths through the bridge, whence the relay-currents are 0nd relay-winding Z2 is energized with a phaseretarded component CI Q which is divided from the first input-current I0, and a phase-advanced component DI; which is divided from the second input current Ir.

For a sine-angle relay having a torque-characteristic as defined in Equation 1 and having exciting currents as defined in Equations 5 and 6, the total relay-torque may be found by taking the algebraic sum of the different pairs of terms, each multiplied by the sine of the angle between the two terms being multiplied, counting the sine positive when the angle of the term in the second 7 current 12 is subtracted from the angle of the Ch, for application to the two winding-currents m Ii and I2, respectively, with the component AIO which flows through the first winding Zi leading the component Clo which flows through theSecond Z2, because of the lower power-factan* multiplying term in the first current I1, according to the'definition of o in the explanation of the derivation of Equation 1. The total torque is thus found to be,

2 sin (15 =ACI sin (a-c) -ADIJ, sin (d-a+0)+ BCI I, sin (b--c+6)--BDI, sin (d-b) 7 If we impose the condition that the relaytorque T is to be independent of the phase-angle 0 between the restraining current It and the operating current Io, the terms containing 0 must cancelout, in the torque-Equation 8, yielding AD sin (da+0) =BC sin (la-0+0) (9) This can be true only if AD=BC (10) and I (da)=(bc) (11) or, from Equations 7a to 7d,

tan"

. tan- 6 This equation may be satisfied in a simple (R,+X1/N)i manner by making (1:11 and 11:0, or, equating D J'VX1+2(RRz)X1/N+R2 R= the same denominator the corresponding tangents, we obtain (17d) (14a) d From an inspection of Equations 17a to 17d, it -l-Rz+R1+R2)X2 (X+X1+X2) (R+R W111 be seen that x+ I+ 2)(R+R2)+( 1+ 2) 2 D=O=B=A (Ri'Rz-FRFF D F( 'FX1+ 2)( 1) +R ,+R1+R2)( +R1)+(X+X1+X2)X1 1 1, (18) (14b) D: A L a Equations 14a and 141) can be satisfied in a sim- 0:3: A A b ple manner, only by making X fix meaning that there are only two diiierent com- 1 a a 20 plex-number operators, A=A,4a. and 3:441 and After substitution from Equations 18, Equa- R2=R1=XUN (15b) tions 5 and 6, which express the relay-currents I1 and I2 in terms of the input-currents I0 and Ir, meaning that the two winding-legs Z1 and Z2 of now reduce to the bridge have identical impedances j A]. Bi AI. AI. b (19) (X1/N+;iX1) or (R1+7'X1) and 1 0+ 7: 0AM- TA Substituting the values 15a and 15b in Equa j =Bj +AL=Aio4b+Air4a (20) non and taking the square roots we have From Equations 17a and 1711, as indeed is evi- (R:r+Xl/N) +(X+X1) dent from Fig. 2,

(R+X1/N) +X1 (15c) X +2XXl+Rm +2RmX1/N=R +2RX1/N (15d) whence the reactance X in the reactance-leg A+B=1 21) whence, from Equations 18,

A A i a A i 2 (Rm-I-jX) of the bridge would have to be cos s n cos smb 1 1a) whence X= i /X1 +2(RR,,)X,/N+(R -R )X, 1

(16a) cos a+cos b= (21b) being an inductive reactance when X is positive, 44) and a capacitive reactance when X is negative; Sm b sm a (21c) while the resistance R in the resistance-leg R of Fr m the relation cos b-i-sin 17:1, d the the bridge would have to be values of cos b and sin 2) found in Equations 21b R=VXHN2+2XX1+X2+Rz2+2RzXl/N X]/N 45 and 210, it follows that (16b) cos a-i-cos a+sin a=l (21d) where X1/N and X1 are respectively the resistwhence ance and the reactance of each of the two iden tical winding-legs Z1 and Z2 of the bridge, and Rx 4: 1 (21 is the resistance of the reactance-leg (RI-H'X) 2 cos a e of thebridge. cos

Equations 15a and 15b and. either Equation Sm 16a or Equation 16b show how to design the 1 1 tan a (21f) bridge for a watt-metric or product-type relay 2 2 having an operating torque which is responsive B=A O b to an operating current I0, and having a restrainc 5 +211 Sm b ing torque which is responsive to a restraining =1 l tan a (21g) current Ir, irrespective of the phase-angle 0 be- 2 2 tween Io and Irwhere the value of tan a is obtainable from Equa- If the design-conditions which are expressed tion 17a, being tan a: I:(R+X1/N)'\ X1 (R Rz) l/ z z+ I/ I (21h) R -{X (1+2/N )+RR +(aRi-R gX /NiX /X +2(RR,,)X /N+R Rz in Equations 15a, 15b and 16a are substituted in the top sign of or i corresponding to positive Equations 7a to 7d, it will be found that (or inductive) values of the reactance X. A=Ala= (Rm-Xl/N):|;j /X +2(RR,)X /N+R R, (17a) (R+R +2X1/N +j( ivX1 +2(RR,)X1/N+R -R2+X0 (R+X1/N) j XI The relay-current Equation 19 and 20, may now B B A the same denominator (17b) be rewntten The :total torque of the relay, as expressed in Equation 8 now reduces to 'T=(Z I, )A sin (ab) 1o -1, tan a 24 Equations 19 and 20, or 22 and 23, show that the network div-ides the operating current Io into two components, Aio and Bio, having the ratio A these two components appearing in the respective relay-currents I1 and 12 which excite the respective windings Z1 and Z2; while the. restraining current Ir ie-divided in the reciprocal ratio E A. This is a new principle in relaying, involving the broad idea of providing a staticnetworkwhich wili divide-the two inputcurrents I and I; in the reciprocally related ratios A B and B A, respectively, to produce the two relay-currents I1 and I2.

Moreover, the magnitudes of the currentratios A and B are equal, only their phase-rotations being different. Furthermore, Equations 22 and 23 show that the phase-angles a and b of the'operators A and B are complementary, so that the in-phase componentof each operator A and B is equal to /2, meaning that the in-phase components of the two components or divided currents Ale and Bio which are divided out of the first input-current IQ (for example) are each equal to one-half of that input-current; while the out-of-phase or quadrature components of these two divided currents AL, and BL) are equal to each other in magnitude, but opposite in sign,

7 withthe first component [misleading the inputcurrent I0, and the secondcomponent BIO lagging behind the input-current 10. A similar statement may be made with respect to the two divided currents BI} and AIr which are divided out of the second input-current Ir, except now it is the second component which is leading.

The conditions just discussed are the conditions for producing a two-torque product-type relay in which the magnitudes of the two opposing torques are responsive only to the magnitudes of the respective input-currents I0 and Ir, regardless of their phase-angles, as shown in Equation 24. While I believe that these are the conditions of the greatest utility for my invention, my bridge-network is nevertheless susceptible of gainful use without the angle-free limitation, that is, with the four component-torques as stated in Equation 8.

Various uses or applications may be made of my novel relay-assembly; or'principle of relayenergization. Three illustrative examples are shown, in'simple forms, in Figs. 3, 4 and 5.

In Fig. 3, external connections are shown, which make use of my relay as a differentialcurrent relay, which is used to compare the magnitudes of the currents in two feeders l3 and I4 which are connected to a common bus IS .in an alternating-current distribution-system. The first input-current I0 is supplied to the relay from a line-current transformer GT1; in the feeder 13, while the other. input-current I1" is supplied to the relay from 'a line-current transformer CT in the feeder I4. Since my relay develops restraint-current I; which is proportional to the sum of the currents traversing the two currenttransformers GT1 and GT2. The primary winding it of the restraint-transformer isprov-ided with a midtap 20, which'is connected to the common terminal 2| of the current-transformers, through the primary winding 22 of an operating transformer 23. The operating transformer 23 has a secondary winding 24 which energizes my relay with an operating current Io which is proportional to the diiference between the linecurrents flowing-in the current-transformers CT1 and GT2. The'operati-ng transformer 23 may, or may not, be saturable: if it is saturable it gives the relay the well-known variable percentage characteristic.

Fig. 5 shows the external connections which illustrate the use of my relay as an impedance relay, or a voltage-restraint overcurrent relay, in which the operating current 10 is derived from a line-current transformer- CT in a protected alternating-current'line section 25, while the restraining current Ir is provided by a line-energized potential-transformer 2%, so that said restraining current is proportional to the linevoltage, In order to make the design flexible in its use and adjustment for special applications, it is preferable to provide means for adjusting the magnitude of one or both of the input-currents I0 and Ir, as by means of a variable-ratio auxiliary transformer 2"! in the line-currentresponsive input-circuit, and a variable resistance .Rv .in the .line-voltage-responsive. input-circult.

The three application-diagrams of Figs. 3, 4 and 5 are intended to be only the simplest sort of diagrams, each illustrative of its particular type of service. It will be understood, of course, that various other external connections may be used. It should be understood, also, that my invention is applicable alike to high-speed relays and slow-speedor time-element relays.

Inthe case of slow-speed voltage-restrained overcurrent relays, with connections of the type shown in Fig. 5, my invention provides several useful design-features which are helpful to the designer in enabling him to secure a considerable variationin the time-characteristic of the relay. Thus, my des-ign'makes provision for'a voltageresponsive restraining-torque, with only a small additional instrument-burden. A' simple adjustment of one or more of the constants of my relay-energizing network. also afiects the operating-characteristics of the relay, by bringing in,

' or removing, a phase-angle response.

9 two bridge-impedances is that they shall have dliferent impedance-angles; and while I have shown a resistance R for one of these impedances, and an inductive reactance +7X for the other, I wish it to be understood that both of these bridge-impedances could be reactive impedances, substituting a capacitor (or negative reactance) for the resistance R, and leaving the inductive branch (RI+9'X) as shown; or the resistance-branch (R) could be left as shown, and the inductive branch (Rm-t-jX) could be replaced by a capacitor having a negative impedance (-7'Xu). In either event, suitable changes will have to be made in Equations 5 and 6 for the relay-currents i1 and I z in terms of the l bridge-constants.

I have already discussed the possibility of using any kind of product-responsive relay-element, which develops a torque proportional to the product of its.two energizing-currents I1 and I2, multiplied by any kind of function of the phase-angle between said currents.

The foregoing and other modifications and substitutions may be made by those skilled in the art, without departing from the essential spirit of my invention, I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

1. A product-responsive relaying element having two windings, means for providing two input-circuits for said relaying element, and a phase-shifting energizing-network connected to the two input-circuits and causing each inputcurrent to be divided into two dissimilar components, the components being respectivey leading and lagging, said network including connections whereby one of said relay-windings is energized with a phase-retarded component divided from the first input-current, and a phase-advanced component divided from the second input-current, while the other relay-winding is energized with a phase-advanced component divided from the first input-current, and a phase-retarded component divided from the second input-current.

2. A product-responsive relaying element having two windings, means for providing two inputcircuits for said relaying element, and a static network for dividing the two input-currents of said input-circuits in the reciprocally related ratios A B and B A, respectively, said network including connections whereby one of said relaywindings is energized in accordance with the A component of the first input-current and the B component of the second input-current, while the other relay-winding is energized in accordance with the B component of the first inputcurrent and the A component of the second input-current, the operators A and B being different complex numbers.

3. The invention as defined in claim 2, char- 10 acterized by the magnitudes of the current-ratios A and B being substantially equal.

4. The invention as defined in claim 2, characterized by the magnitudes of the current-ratios A and B being substantially equal, and the inphase components of the two complex numbers A and B being equal to each other, while the out-of-phase components are equal in magnitude and opposite in sign, one leading and the other lagging the associated input-current.

5. The invention as defined in claim 2, characterized by the operators A and B having the following values,

H Nair- B=- j 5 tan a 6. In combination: a product-responsive relaying element having two windings; two impedances having differing impedance-angles; a bridge-circuit connection including the two relaywindings in opposite legs, and including the two impedances in the two remaining legs of the bridge; and two alternating-current input-circuits connected to the respective diagonal corners of the bridge.

7. The invention as defined in claim 6, characterized by the bridge-impedances being so related that the relay-torque is substantially independent of the phase-angle between the two input-currents.

8. The invention as defined in claim 6, characterized by one of said impedances being a resistance device, and the other impedance being a reactance device.

9. The invention as defined in claim 6, characterized by the relay-windings having identical impedances (R1+;iX1), one of the impedancelegs of the bridge being a resistance R, and the other impedance-leg having an impedance (R@+y'X), the reactive component of which is being an inductive reactance when X is positive, and a capacitive reactance when X is negative.

10. The invention as defined in claim 6, characterized by the relay-windings having identical impedances (Rl-HXi), one of the impedancelegs of the bridge having an impedance (Re-H'X) and the other impedance-leg being a resistor having a resistance REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,426,013 Goldsborough Aug. 19, 1947 

